2-Nitroxymethyl and 2,6-bis-nitroxymethyl-pyridine compounds having vasodilating activity

ABSTRACT

This invention relates to pyridylalkyl nitrate compound and a salt thereof. More particularly, it relates to a new pyridylalkyl nitrate compound and a pharmaceutically acceptable salt thereof which have vasodilating activities, to process for the preparation thereof, and to a pharmaceutical composition comprising the same for therapeutical treatment of cardiovascular disorder in human being.

With regard to the states of the arts in this field, for example, thefollowing pyridylalkyl nitrate compound is known. ##STR1##

One object of this invention is to provide the new and usefulpyridylalkyl nitrate compound and a pharmaceutically acceptable saltthereof, which have stronger activity as compared with the knowncompounds, for example, as shown above.

Another object of this invention is to provide process for thepreparation of said pyridylalkyl nitrate compound and the salt thereof.

A further object of this invention is to provide a useful pharmaceuticalcomposition comprising, as an active ingredient, said pyridylalkylnitrate compound or the pharmaceutically acceptable salt thereof, whichis useful, as a vasodilator agent.

Still further object of this invention is to provide a therapeuticalmethod for treatment of cardiovascular disorder such as coronaryinsufficiency, angina pectoris or myocardial infarction.

The pyridylalkyl nitrate compound of this invention can be representedby the following formula: ##STR2## wherein R¹ is hydrogen, lower alkyl,halogen or nitroxy(lower)alkyl,

one of R² and R³ is mono (or di)-nitroxy(lower)alkyl and

the other of R² and R³ is hydrogen or halogen.

According to this invention, the object compound (I) can be prepared bythe process as illustrated by the following scheme.

    ______________________________________                                        Process                                                                        ##STR3##                                                                                   ##STR4##                                                                                   ##STR5##                                           or salts thereof or       or salts thereof                                    its reactive derivative                                                       at the hydroxy group(s)                                                       on hydroxy(lower)alkyl                                                        group(s)                                                                      ______________________________________                                    

wherein

R¹, R² and R³ are each as defined above,

R_(a) ¹ is hydrogen, lower alkyl, halogen or hydroxy(lower)alkyl,

one of R_(a) ² and R_(a) ³ is mono (or di)-hydroxy(lower)alkyl and theother of R_(a) ² and R_(a) ³ is hydrogen or halogen.

Suitable pharmaceutically acceptable salts of the object compounds (I)are conventional non-toxic salt and include an acid addition salt suchas an organic acid salt (e.g. acetate, trifluoroacetate, maleate,tartrate, methanesulfonate, benzenesulfonate, formate, toluenesulfonate,etc.), an inorganic acid salt (e.g. hydrochloride, hydrobromide,hydroiodide, sulfate, nitrate, phosphate, etc.), or a salt with an aminoacid (e.g. arginine, aspartic acid, glutamic acid, etc.), or the like.

In the above and subsequent descriptions of the present specification,suitable examples and illustrations of the various definitions which thepresent invention include within the scope thereof are explained indetails as follows.

The term "lower" is intended to mean 1 to 6 carbon atoms, unlessotherwise indicated.

Suitable "lower alkyl" and "lower alkyl" moiety in the terms"nitroxy(lower)alkyl", "mono (or di)-nitroxy(lower)alkyl","hydroxy(lower)alkyl" and "mono (or di)-hydroxy(lower)alkyl" is onehaving 1 to 6 carbon atom(s) and may include methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, pentyl, tert-pentyl, hexyl andthe like, and preferably one having 1 to 4 carbon atom(s).

Suitable halogen may include chlorine, bromine, fluorine and iodine.

Suitable reactive derivative at the hydroxy group(s) on"hydroxy(lower)alkyl" and "mono (or di)-hydroxy(lower)alkyl" may includean acid residue such as halogen as mentioned above or the like.

Process for the preparation of the pyridylalkyl nitrate compound (I) isexplained in detail in the following.

A compound (I) or salts thereof can be prepared by reacting a compound(II) or salts thereof or its reactive derivative at the hydroxy group(s)on hydroxy(lower)alkyl group(s) with a nitrating agent.

Suitable salts of the compound (II) can be referred to the ones asexemplified for the compound (I).

Suitable nitrating agent used in the process may include nitric acid, acombination of acetic anhydride and nitric acid or a combination ofconcentrated sulfuric acid and nitric acid, or the like.

The reaction temperature is not critical and the reaction is usuallycarried out under cooling or at ambient temperature. The reaction isusually carried out without solvent or in a solvent such as acetic acidor other conventional solvents which do not adversely affect thereaction.

Thus obtained compound (I) may be converted into pharmaceuticallyacceptable salts thereof by conventional manner.

For therapeutical purpose, the pyridylalkyl nitrate compound (I) isadministered in daily dose of 0.01 to 50 mg, preferably 0.1 to 10 mg.

The pharmaceutical compositions of this invention comprise, as an activeingredient, the pyridylalkyl nitrate compound (I) or pharmaceuticallyacceptable salt thereof in an amount of about 0.01 mg to about 10 mg,preferably about 0.01 mg to about 5 mg per dosage unit for oral andparenteral use.

One skilled in the art will recognize that the amount of the activeingredient in the dosage unit form may be determined by considering theactivity of the ingredient as well as the size of the host human being.The active ingredient may usually be formulated in a solid form such astablet, granule, powder, capsule, troche, lozenge or suppository, or asuspension or solution form such a syrup, injection, emulsion, lemonade,etc. and the like. A pharmaceutical carrier or diluent includes solid orliquid non-toxic pharmaceutically acceptable substances. Examples ofsolid or liquid carriers or diluents are lactose, magnesium stearate,terra alba, sucrose, corn starch, talc, stearic acid, gelatin, agar,pectin, acacia, peanut oil, olive oil or sesame oil, cacao butter,ethyleneglycol or the other conventional ones. Similarly, the carrier ordiluent may include a time delay material such as glyceryl monostearate,glyceryl distearate, a wax and the like.

For the purpose of showing the utility of the compound (I), thepharmacological test results of some representative compounds are shownas follows.

EFFECT ON ISOLATED CORONARY ARTERY Test Method

The large and small coronary arteries, 2.0 and 0.5 mm in outsidediameter respectively, were removed from pentobarbital-anesthetizeddogs. Spiral strips approximately 15 and 5 mm in length were cut fromthe large and small arteries respectively, and suspended in an organbath containing Tyrode's solution at 37° C., aerated with a gas mixtureof 95% oxygen and 5% carbon dioxide. The tonus of the strips wasrecorded on a polygraph with a force-displacement transducer. After theinitial resting tension was adjusted to 1.0 g for the large artery and100 mg for the small artery, potassium chloride 35 mM was added to theorgan bath to increase the tonus of the large arterial strips to 1.4-1.6g and the small arterial strips to 120-140 mg. The cumulativeconcentrations of the test compounds were then added, and finallypapaverine 10⁻⁴ M was given to determine maximum relaxation. ED₅₀ valueswere calculated by interpolation from the mean cumulative dose-activitycurves (effect of papaverine 10³¹ 4 M=100%).

Test Compound

Compound A: 3-Nitroxymethylpyridine (reference compound)

Compound B: 2,6-Bis(nitroxymethyl)pyridine

Compound C: 4-(3-Nitroxypropyl)pyridine

Compound D: 2-Nitroxymethyl-6-chloropyridine

Compound E: 2,6Bis(nitroxymethyl)-4chloropyridine

Test Results

The values are shown in the following Table.

As clear from the test results in the Table, especially from S/L values,it is evident that the compounds of the present invention ischaracterized by possessing potent and selective dilating activity onlarge coronary artery as compared with small coronary artery, whichmeans that the compounds of the present invention are useful fortreatment of cardiovascular disorder.

                  TABLE                                                           ______________________________________                                        ED.sub.50 g/ml                                                                Compound                                                                              Large (L)     Small (S)   S/L                                         ______________________________________                                        A       8.0 × 10.sup.-8                                                                       1.9 × 10.sup.-6                                                                     23.8                                        B       4.0 × 10.sup.-9                                                                       2.25 × 10.sup.-7                                                                    56.3                                        C       1.25 × 10.sup.-8                                                                      >1.0 × 10.sup.-5                                                                    >800                                        D       6.7 × 10.sup.-9                                                                       6.2 × 10.sup.-6                                                                     925                                         E       2.75 × 10.sup.-9                                                                      2.30 × 10.sup.-7                                                                    83.6                                        ______________________________________                                    

The following Examples are given for the purpose of illustrating thepresent invention.

Preparation of the object compounds for this invention EXAMPLE 1

Fuming nitric acid (4.1 ml) was added dropwise to acetic anhydride (13.5ml) with stirring at 5° to 10° C. After the mixture was stirred for 30minutes at 5° C., 2-hydroxymethylpyridine nitrate (3.3 g) was added insome portions thereto. The resulting mixture was stirred for 3 hours at0° to 5° C. A mixture of benzene (15 ml) and n-hexane (30 ml) was addedthereto. The mixture formed two layers. The upper layer was separatedand discarded while the remaining lower layer was again treated with amixture of benzene (10 ml) and n-hexane (10 ml). After the separation ofthe layers, the lower layer was again separated, mixed with benzene (10ml) and made homogeneous with isopropyl alcohol (10 ml). The resultingmixture was allowed to stand overnight in a refrigerator to givecrystals. The crystals were collected by filtration and washed withdiethyl ether to give white crystals of 2-nitroxymethylpyridine nitrate(2.4 g), mp. 75° to 77° C.

IR (Nujol): 2450, 2050, 1645, 1430, 1280, 840 cm⁻¹

NMR (DMSO-d₆, δ): 5.85 (2H, s), 7.65-8.1 (2H, m), 8.1-8.5 (1H, m), 9.85(1H, dd, J=5.5 Hz, 1 Hz), 14.95 (1H, s)

Analysis for C₆ H₆ N₂ O₃.HNO₃ : Calcd: C: 33.19; H: 3.25; N: 19.35;found: C: 32.86; H: 3.17; N: 19.31

EXAMPLE 2

Fuming nitric acid (5 ml) was added dropwise to acetic anhydride (9.5ml) with stirring at 5° to 10° C. 2,6-Bis(hydroxymethyl)pyridine (6.95g) was added thereto. The resulting mixture was stirred for 20 minutesat 5° to 10° C. and for additional 1.5 hours at 20° C., and then pouredinto a mixture of ethyl acetate (40 ml) and ice-water (60 ml). Theresulting mixture was neutralized with aqueous potassium carbonatesolutions. The ethyl acetate layer was separated, washed with water,dried over anhydrous magnesium sulfate, and concentrated under reducedpressure. The residue obtained was subjected to column chromatography onaluminum oxide (30 g) and eluted with toluene. The fractions containingthe desired compound were concentrated under reduced pressure to givecolorless viscous oil of 2,6-bis(nitroxymethyl)pyridine (5.1 g).

IR (Nujol): 1635, 1600, 1460, 1285, 1160, 970, 850 cm⁻¹

NMR (CDCl₃, δ): 5.50 (4H, s), 2.34 (2H, d, J=8 Hz), 7.78 (1H, t, J=8 Hz)

Analysis for C₇ H₇ N₃ O₆ : calcd: C: 36.69; H: 3.08; N: 18.34; found: C:36.97; H: 3.16; N: 18.64

EXAMPLE 3

The following compounds were obtained according to similar manners tothose of Examples 1 and 2.

(1) 2-(2-Nitroxyethyl)pyridine nitrate, mp. 49°-52° C.

IR (Nujol): 2560, 2110, 1635, 1625, 1405, 1315, 1280 cm⁻¹

NMR (DMSO-d₆, δ): 3.51 (2H, t, J=6 Hz), 4.99 (2H, t, J=6 Hz), 7.8-8.3(2H, m), 8.59 (1H, dt, J=8 Hz, 2 Hz), 8.93 (1H, dd, J=6 Hz, 2 Hz), 13.45(1H, s)

Analysis for C₇ H₈ N₂ O₃.HNO₃ : calcd: C: 36.37; H: 3.92; N: 18.18;found: C: 35.97; H: 3.86; N: 18.19

(2) 2-(1-Nitroxymethyl-2-nitroxyethyl)pyridine hydrochloride, mp.111°-112° C.

IR (Nujol): 2420, 1620, 1460, 1275, 990, 870, 840, 750 cm⁻¹

NMR (DMSO-d₆, δ): 2.32 (1H, quintet, J=6 Hz), 5.14 (4H, d, J=6 Hz), 7.90(1H, m), 8.14 (1H, d, J=8 Hz), 8.47 (1H, dt, J=8 Hz, 2 Hz), 8.87 (1H,dd, J=4 Hz, 2 Hz), 18.20 (1H, brs)

Analysis for C₈ H₉ N₃ O₆.HCl: calcd: C: 34.36; H: 3.60; N: 15.03; Cl:12.68; found: C: 34.13; H: 3.61; N: 14.78; Cl: 12.50

(3) 2,6-Bis(nitroxymethyl)-4-chloropyridine, mp. 30°-35° C.

IR (Nujol): 1638, 1582, 1278, 1043, 847, 756 cm⁻¹

NMR (CDCl₃, δ): 5.52 (4H, s), 7.35 (2H, s)

Analysis for C₇ H₆ ClN₃ O₆ : calcd: C: 31.89; H: 2.29; N: 15.94; found:C: 32.06; H: 2.29; N: 16.12

(4) 4-(3-Nitroxypropyl)pyridine

IR (Nujol): 1625, 1410, 1275, 865, 800, 760 cm⁻¹

NMR (CCl₄, δ): 1.7-2.4 (2H, m), 2.73 (2H, t, J=7 Hz), 4.41 (2H, t, J=7Hz), 7.03 (2H, d, J=5 Hz), 8.39 (2H, d, J=5 Hz)

Analysis for C₈ H₁₀ N₂ O₃ : calcd: C: 52.74; H: 5.53; N: 15.38; found:C: 53.19; H: 5.64; N: 15.30

(5) 2-Nitroxymethyl-6-methylpyridine hydrochloride, mp. 65°-68° C.

IR (Nujol): 1635, 1275, 1171, 999, 847, 837 cm⁻¹

NMR (CCl₄, δ free form): 2.48 (3H, s), 5.40 (2H, s), 7.02 (1H, d, J=8Hz), 7.04 (1H, d, J=8 Hz), 7.49 (1H, t, J=8 Hz)

Analysis for C₇ H₈ N₂ O₃.HCl: calcd: C: 41.09; H: 4.43; N: 13.69; found:C: 40.80; H: 4.42; N: 13.68

(6) 2-Nitroxymethyl-6-chloropyridine

IR (Nujol): 1636, 1585, 1563, 1439, 1281, 1160, 1138, 985, 846, 785 cm⁻¹

NMR (CCl₄, δ): 5.47 (2H, s), 7.15-7.45 (2H, m), 7.69 (1H, dd, J=8.5 Hz,J=6 Hz)

Analysis for C₆ H₅ ClN₂ O₃ : calcd: C: 38.22; H: 2.67; N: 14.86; found:C: 37.97; H: 2.75; N: 14.95

What we claim is:
 1. A pyridylalkyl nitrate compound selected from thegroup consisting of:2,6-bis(nitroxymethyl)pyridine;2,6-bis(nitroxymethyl)-4-chloropyridine; and2-nitroxymethyl-6-chloropyridine.
 2. The compound of claim 1, which is2,6-bis(nitroxymethyl)pyridine.
 3. The compound of claim 1, which is2,6-bis(nitroxymethyl)-4-chloropyridine.
 4. The compound of claim 1,which is 2-nitroxymethyl-6-chloropyridine.
 5. A vasodilatingpharmaceutical composition comprising an effective amount of a compoundof claim 1 or pharmaceutically acceptable salt thereof in associationwith a pharmaceutically acceptable, substantially non-toxic carrier orexcipient.